* Euro zone finance ministers in third attempt at Greek deal
* Investors take profits after last week's strong finish
* Qatar cashes in its warrants in Barclays, shares dip
* Knight Capital in talks for unit sale; shares jump
* Indexes off: Dow 0.7 pct; S&P 0.6 pct; Nasdaq 0.2 pct
By Edward Krudy
NEW YORK, Nov 26 (Reuters) - U.S. stocks eased on Monday as a mixed start to the holiday shopping season, caution over Greek aid talks and budget discussions in Washington gave investors reason to pause after Wall Street posted its best week in over five months.
While holiday shopping appeared to be off to a good start, analysts cautioned against reading too much into one weekend's numbers. Retailers need to sustain the initial burst through the November-December holiday season, which can account for a third of annual sales and 40 to 50 percent of profits for the year.
Shares in department store operator Macy's Inc, which offered consumers deep discounts on Black Friday, fell 3.6 percent to $40.22. The SPDR S&P retail exchange-traded fund fell 1.3 percent to $62.39.
"The underwhelming performance of retailers in general is hurting the market," said Michael James, a senior trader at Wedbush Morgan in Los Angeles. "Retail is certainly seeing a mixed bag."
Investors continued to chew over two of the greatest overhangs for markets. Euro zone finance ministers and the International Monetary Fund will seek to unfreeze the second bailout package for Greece on Monday. At the same time, U.S. lawmakers have made little progress in the past 10 days toward a compromise to avoid the harsh tax increases and government spending cuts schedule to start in January.
"Friday was a big day in the stock market," said Tim Ghriskey, chief investment officer at Solaris Group in Bedford Hills, New York. "So it's not surprising at all to see some profit-taking on that."
The Dow Jones industrial average dropped 88.58 points, or 0.68 percent, to 12,921.10. The Standard & Poor's 500 Index fell 8.40 points, or 0.60 percent, to 1,400.75. The Nasdaq Composite Index lost 5.84 points, or 0.20 percent, to 2,961.01.
Total spending for the Black Friday long weekend rose 12.8 percent from last year, to $59.1 billion, from last year, according to the National Retail Federation. That pace was down from the prior year's 16.4 percent increase.
Black Friday's online sales topped $1 billion for the first time ever as more consumers used the Internet do their early holiday shopping, comScore Inc said on Sunday.
Major indexes ended last week with gains of 3 to 4 percent, recovering some of their losses following an 8 percent correction since September. The Dow and S&P 500 both closed above key technical levels for the first time since Nov. 6, which could provide additional support. The Dow ended above 13,000, while the S&P broke above 1,400.
In company news, shares of Knight Capital Group Inc jumped 10.4 percent to $2.75. A source familiar with the matter on Saturday said the company is in talks about possibly selling its market-making operation, its largest and most profitable business, but it is not known if a deal will happen. Knight's chief executive, in an internal memo, said the company currently is in talks with at least two firms on the possible sale of its largest business unit, but would only pursue a deal if it created value for its shareholders and clients.
Qatar has cashed in its remaining warrants in Britain's Barclays Plc, a move that should yield a $280 million profit. The warrants have not yet been converted, but conversion would dilute the holding of shares by other investors. U.S.-listed shares of Barclays fell 5.6 percent to $15.37.
Apple Inc has asked a federal court to add six more products to its patent infringement lawsuit against Samsung Electronics Co, including the Samsung Galaxy Note II, in the latest move in an ongoing legal war between the two companies. Apple shares were up 1.7 percent at $581.